It is a bit annoying that the final boss' tentacle attack doesn't deal enough damage to instantly kill you if you have enough health, yet getting hit by it causes the boss to fully heal.
I found cheese for the hard badge: Lose your life on all 16 minigames except for a single easy one, and then play that single minigame until you get to the 5x multiplier. I got it easily with the green ball minigame.
In case it helps anyone, there is a way to upgrade 5/10x without holding Shift or Ctrl. Step 1: hold Shift or Ctrl. Step 2: click out of the game. Step 3: let go of Shift or Ctrl. Step 4: enjoy. Can be undone by pressing Shift or Ctrl again.
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